1. Field of the Invention
The present invention relates to a mounting structure for a hydrostatic unit and in particular to a mounting structure for mounting a hydrostatic unit within a larger transmission housing.
2. Description of Related Art
When mounting a hydrostatic unit within a transmission housing, it is desirable to isolate the hydrostatic unit from the housing to avoid transmission of noise and vibration from the hydrostatic unit to the transmission housing. One method of doing so is disclosed in U.S. Pat. No. 5,345,839 where the hydrostatic unit is supported on transversely spaced rods. The rods extend through and are supported by the transmission housing. At each of the rod ends, a rubber bushing is provided between the rod and the transmission housing to reduce the noise transmitted from the hydrostatic unit. A problem with this design is that the support rods require additional space within the overall structure of the transmission housing. Furthermore clamping bores are formed in the hydrostatic unit that fit over the support rods and clamp thereto. Tightening of the clamps onto the rods requires additional hardware and is difficult to assemble, as it must be done inside the transmission housing.
Accordingly, it is an object of the present invention to provide a mounting structure for the hydrostatic unit that maintains or improves the noise and vibration isolating characteristics while reducing the space necessary for the mounting structure.
It is further object of the invention to provide a mounting structure that enables the hydrostatic unit to be mounted in the transmission housing without requiring the assembler to reach into the interior of the transmission housing to install or tighten fasteners inside the transmission housing.
The mounting structure of the present invention uses a plurality of mounting pins supporting and positioning the hydrostatic unit in the transmission housing. The pins each have a stud portion projecting into a bore in the case of the hydrostatic unit. An externally threaded portion of the pin is threaded into a bore in the transmission housing to mount the pin to the transmission housing. A flange on the pin extends radially outward to overlie and engage the transmission housing surrounding the bore to limit the extent to which the pin is threaded into the transmission housing. The stud is thus positioned relative to the transmission housing whereby the hydrostatic unit is supported and positioned within the transmission housing.
The mounting pins are also provided with an O-ring groove to receive an O-ring. The O-ring seals the transmission housing against leaks and contamination.
Preferably two mounting pins are provided on each side of the transmission to fully support and position the hydrostatic unit within the transmission housing. The pins have an internal socket to drive the mounting pins into the transmission housing. The internal socket reduces the projection of the mounting pins beyond the surface of the transmission housing to facilitate packaging of the transmission within a vehicle structure.